Post-processing data

Plotting 3D data

Three dimensional flow fields are stored in Plot3D and/or VTK format and can be visualized using Paraview, or Tecplot.

Post-processing flow statistics

Mean flow statics are stored in raw format in the file stat.bin. To post-process it, use the post-processing program available in the folder tools/postpro. Compile the tool by typing,

$ make

This will produce the executable postpro.exe.

Different files will be printed depending on the flow case that has been run.

Channel flow

Copy the executable postpro.exe to the case folder you want to post-process and run:

$ ./postpro.exe

This will print the post-processed flow statistics in the folder POSTPRO/, which will contain the files channinfo.dat and channstat.prof

channinfo.dat

The file channinfo.dat contains

• \(Re_\tau=u_\tau h/\nu_w\), friction Reynolds number, where \(h\) is the channel half width and \(\nu_w\) the kinematic viscosity at the wall

• \(\overline{\rho}_w\) mean wall density

• \(u_\tau/u_b\), ratio between friction and bulk flow velocity

• \(C_f=2\overline{\tau}_w/(\rho_b u_b^2)\) skin-friction coefficient based on the mean wall shear stress, bulk flow velocity and bulk fluid density

channstat.prof

The file channstat.prof contains mean profiles of channel flow in the following format:

1. \(y/h,\quad\) wall-normal coordinate normalized with the channel half width

2. \(y^+,\quad\) wall-normal coordinate in viscous units

3. \(y_{TL}^+,\quad\) wall-normal coordinate transformed according to Trettel and Larsson [13] in viscous units

4. \(\widetilde{u}/u_b,\quad\) mean streamwise velocity normalized by the bulk flow velocity

5. \(u^+,\quad\) mean streamwise velocity in viscous units

6. \(u_{VD}^+,\quad\) mean streamwise velocity transformed according to van Driest [3] in viscous units

7. \(u_{TL}^+,\quad\) mean streamwise velocity transformed according to Trettel & Larsson [13] in viscous units

8. \(\overline{\rho}/\overline{\rho}_w,\quad\) mean density normalized by the mean wall density

9. \(\overline{\tau}_{11}/\tau_w,\quad\) normal Reynolds stress component 11, scaled by density, in viscous units

10. \(\overline{\tau}_{22}/\tau_w,\quad\) normal Reynolds stress component 22, scaled by density, in viscous units

11. \(\overline{\tau}_{33}/\tau_w,\quad\) normal Reynolds stress component 33, scaled by density, in viscous units

12. \(\overline{\tau}_{12}/\tau_w,\quad\) Reynolds shear stress component 12, scaled by density, in viscous units

13. \(\overline{T}/T_w,\quad\) mean temperature normalized by the wall temperature

14. \(\overline{\rho_w}/\rho_w,\quad\) mean density normalized by wall density

15. \(\overline{T^{'2}}/T_w^2,\quad\) temperature fluctuations normalized by the wall temperature

16. \((\overline{T}-T_w)/T_\tau,\quad\) mean temperature in viscous units

17. \(\overline{T^{'2}}/T_\tau^2,\quad\) temperature fluctuations in viscous units

18. \(y_{V}^+,\quad\) wall-normal coordinate transformed according to Volpiani et al. [14], in viscous units

19. \(u_{V}^+,\quad\) mean streamwise velocity transformed according to Volpiani et al. [14], in viscous units

Boundary layer

Copy the executable postpro.exe to the case folder you want to post-process. Create an ASCII file named bl_profiles.dat. The file should contain two lines: report the number of profiles you want to extract on the first line, and the corresponding indices of the x coordinate on the second line. For instance, the following file

2
500 1000

will extract boundary layer statistics at two locations, corresponding to locations \(x_{i=500}\) and \(x_{i=1000}\).

Run the post-processing tool by typing:

$ ./postpro.exe

The post-processing routine will create the folder POSTPRO, containing the files cf.dat and stat_nnnnn.dat, where nnnnn is the number of profiles.

cf.dat

The file cf.dat contains the boundary layer characteristics as a function of the streamwise direction:

1. \(x/\delta_0,\quad\) streamwise coordinate normalized by inflow boundary layer thickness

2. \(Cf=\overline{\tau}_w/(\rho_w U_\infty^2),\quad\) skin friction coefficient

3. \(Re_\tau=\delta_{99}/\delta_v,\quad\) friction Reynolds number

4. \(H,\quad\) shape factor

5. \(H_{inc},\quad\) incompressible shape factor

6. \(\delta_{99},\quad\) boundary layer thickness

7. \(\delta^*,\quad\) displacement thickness

8. \(\theta^*,\quad\) momentum thickness

9. \(u_\tau/U_\infty,\quad\) friction velocity normalized by free stream velocity

10. \({Re_\theta}_{inc}=\rho_\infty U_\infty\theta_{inc}/\mu_\infty,\quad\) Reynolds number based on incompressible momentum thickness

11. \({C_f}_{inc},\quad\) Skin friction coefficient transformed according to van Driest II transformation [4]

12. \({Re_\theta}=\rho_\infty u_\infty\theta/\mu_w\quad\), Reynolds number based on momentum thickness, and viscosity at the wall

13. \(p_{rms}/\tau_w\) Pressure rms at the wall in viscous units

stat_nnnnn.dat

The files stat_nnnnn.dat contain the boundary layer profiles in the following format:

1. \(y/\delta_{99},\quad\) wall-distance normalized by local boundary layer thickness

2. \(y^+,\quad\) wall-distance in viscous units

3. \(\widetilde{u}^+,\quad\) streamwise velocity in viscous units

4. \(u_{VD}^+,\quad\) streamwise velocity transformed according to van Driest:cite:p:vanDriest1955, in viscous units

5. \(\overline{\tau}_{11}/\tau_w,\quad\) normal Reynolds stress component 11, scaled by density, in viscous units

6. \(\overline{\tau}_{22}/\tau_w,\quad\) normal Reynolds stress component 22, scaled by density, in viscous units

7. \(\overline{\tau}_{33}/\tau_w,\quad\) normal Reynolds stress component 33, scaled by density, in viscous units

8. \(\overline{\tau}_{12}/\tau_w,\quad\) Reynolds shear stress component 12, scaled by density, in viscous units

9. \(\overline{\rho}/\overline{\rho}_w,\quad\) mean density scaled by the wall density

10. \(\overline{p^{'2}}/\tau_w,\quad\) pressure fluctuations in wall units

11. \(y_{TL}^+,\quad\) wall-normal coordinate transformed according to Trettel and Larsson [13], in viscous units

12. \(u_{TL}^+,\quad\) mean streamwise velocity transformed according to Trettel and Larsson [13], in viscous units

13. \(y_{V}^+,\quad\) wall-normal coordinate transformed according to Volpiani et al. [14], in viscous units

14. \(u_{V}^+,\quad\) mean streamwise velocity transformed according to Volpiani et al. [14], in viscous units